The present invention is generally directed to a delustered fiber sorbent and a method of using the delustered fiber sorbent in the removal of hydrocarbon products from a contaminated material, and more specifically, to the removal of hydrocarbon products contaminating the surface of an aqueous medium, by employing a wadded mass of delustered hydrophobic and lipophilic fibers that are placed in contact with the contaminated surface so as to sorb the hydrocarbon products.
The widespread use of petroleum products is accompanied by the almost statistical certainty that accidents involving the release of petroleum products into the environment will occur. In recognition of the deleterious effects such spills can have on the environment, many governmental agencies have drafted regulations mandating that spill response equipment, including sorbent material, be readily available to contain and collect the spilled material, to minimize the deleterious environmental effects of the petroleum products.
Due to increasing globalization, many nations are involved in transporting extremely large volumes of raw petroleum and petroleum products in tanker ships via waterways, such as lakes, rivers, and, oceans and in tanker vehicles or railcars that travel adjacent to waterways. Accidents involving large volumes of petroleum, such as the Exxon Valdez incident in Alaska, have generated tremendous concern among the public. In response to such incidents, various governmental agencies have adopted strict spill response regulations to prevent, or at least minimize, the damage from a future large scale spill on waterways. Such regulations often provide for the creation of spill response teams that are required to stockpile large quantities of sorbent material at locations that are associated with high traffic of large volumes of petroleum products. In recognition of the need for sufficient quantities of sorbent material to be readily available at many different locations, it would be desirable to provide an efficient, inexpensive, and lightweight sorbent product that can be used to remove petroleum and other hydrocarbon products from contaminated surfaces, including the surface of a body of water.
The prior art includes many different types of sorbent products. Sorbents work either by absorption, adsorption, or both. Absorption is a process in which a material is taken in through pores or interstices of another material, while adsorption is a process in which a material is accumulated on the surface of a solid or liquid. In general, sorbents that function via both absorption and adsorption tend to be more effective in enabling a petroleum or other hydrocarbon spilled on a surface to be collected and removed. It would therefore be desirable to provide a sorbent that is sufficiently economical and environmentally friendly to be used on the surface of a body of water, and which both adsorbs and absorbs petroleum and other hydrocarbon products.
The prior art recognizes that an effective sorbent material should have a high affinity for sorbing the target material to be collected and removed, and that the sorbent should preferably sorb a relatively large amount of the target material per unit weight of the sorbent. Effective sorbents tend to have a relatively great surface area, so as to encourage contact of the sorbent with the target material. With respect to sorbents employed to recover hydrocarbons from the surface of a body of water, a low specific gravity ensures that the sorbent will float on the water surface, both before and after hydrocarbons have been sorbed.
U.S. Pat. No. 5,304,311 discloses an elastomeric ethylene/alpha-olefin copolymer, optionally copolymerized with a diene, that can be applied in a granular subdivided form. After absorbing the hydrocarbon product, the sorbent forms a jelly-like, homogeneous mass, which can then be removed by conventional mechanical means. The jelly-like mass is cohesive, and modest wave action will not disperse the sorbent beyond a desired area of treatment. While effective, such a material requires a finite contact period to transition from the granular state to the jelly-like mass. Sorbents such as that disclosed in the above-referenced patent are often referred to as solidifiers, as they change oil from a liquid to a solid. Unlike sorbents, solidifiers do not release solidified oils under pressure, ensuring that the xe2x80x9cdripping-spongexe2x80x9d effect is eliminated, which in some situations may be desirable. However, there are many instances in which it may be desirable to recover and recycle any petroleum product that has been picked up by a sorbent. A French study of oil solidifying agents concluded that the following problems are associated with solidifiers: (1) the reaction of cross-linkers (in the solidifier) with portions of oil that are in direct contact results in non-uniform solidification; (2) the non-selective nature of cross-linkers that will solidify anything that contains hydrocarbons, including weeds and other organic matters; (3) mechanical difficulty in removing a solidified spill, since it cannot be pumped; and, (4) the large amount of solidifier that is required to cross-link and solidify an oil spill. Finally, due primarily to the cost of the ingredients, such as the cross-linkers required to facilitate the solidifying reaction, solidifiers such as that disclosed in the above-referenced patent tend to be somewhat expensive. It would be desirable to provide a more rapidly acting sorbent material, which is less costly to produce, requires a relatively small volume of sorbent to be employed, and which can be processed to recover sorbed hydrocarbons if desired.
In addition to granular solidifying sorbents, the prior art also discloses the use of polymeric fibers and expanded polymeric foams to sorb petroleum products. U.S. Pat. No. 5,407,575 describes a relatively small two-part sorbent pad having a flat, chemically treated polyethylene foam inner core completely surrounded by a flexible, durable, chemically treated polypropylene fabric cover. The sorbent pad is intended to float on top of petroleum covered water and to soak up the petroleum or oil and hold it within the inner core until it can be removed by squeezing the sorbent pad between rollers, thereby recovering the oil for storage in a container. The sorbent pad can then be returned to the water to pick up more petroleum. The sorbent pad is chemically treated to increase the pad""s ability to attract and hold oil by both adsorption and absorption and to further increase the pad""s ability to repel water. This treatment necessitates extra processing in the manufacture of the sorbent, thereby increasing its cost. While the sorbent pad is useful, it would be desirable to provide a lower cost sorbent that are not in a pad configuration and thus can be carried or stored in large quantities as needed, in order to be able to treat massive oil spills, such as those associated with an oil tanker running aground and breaking apart.
In addition to employing polymeric granules and foams, the prior art also discloses using polymeric fibers as a petroleum sorbent. Many patents disclose various filters for either cleaning oil, or removing oil from water, which include polymeric fibers. Fibers that have little cotton or cellulose content are hydrophobic, and have a high affinity for petroleum. Examples of patents that disclose the use of polymeric fibers in a filter include U.S. Pat. No. 4,329,226, which discloses a filter apparatus for reconditioning oil and uses cotton fibers, polyester fibers, and wood (specifically aspen) fibers to filter dirty oil. U.S. Pat. No. 4,707,269 describes a non-woven hydrophobic fabric used to separate oil and water mixtures, and U.S. Pat. No. 5,855,784 describes a sheet filter formed of thermally bonded polymer fibers. U.S. Pat. No. 5,993,675 describes a fuel filter that includes polymeric micro-fibers to remove water from a hydrocarbon fuel.
Regulatory and governmental agencies are increasingly focusing on the use of environmental friendly products. In addition, there is a general preference by many such agencies to purchase recycled products over new products, whenever possible. Thus, it would be desirable to provide a sorbent that can be produced from scrap or recycled materials, with minimal required processing.
In addition to using polymeric fibers for filters, such fibers have also been employed as sorbents. U.S. Pat. No. 5,080,956 describes a laminate mat designed to be placed underneath machinery to catch oil drips machinery and comprising flow directing means, and an adsorbent layer made from a mat of OLEFIN(trademark) fiber. Polymeric fibers have also been used as fillers for booms and pillows, most often in the form of a mass of spun fiber inserted into a boom or pillow. While these sorbent products are functional, they employ virgin fiber, and thus offer no advantage for those seeking to use a recycled product. It would therefore be desirable to provide a hydrophobic and lipophilic fiber-based sorbent product that can be produced more economically than currently available sorbents, and which can be made from recycled material. It should be noted that particularly in respect to recycled fibers, there is a perception that recycled fibers are generally poorer in quality than virgin fiber. It would therefore be desirable to provide a recycled fiber based sorbent that is as effective as, if not more effective than, virgin fiber-based sorbents.
The present invention preferably employs synthetic fiber waste that would otherwise be disposed of in a landfill or other waste facility. While virgin synthetic fiber could be employed in the present invention, additional processing steps would be required to achieve the greater sorption efficiency that are provided by waste fibers from the textile industry. Note that synthetic fibers are naturally hydrophobic and lipophilic (i.e., they exhibit a natural affinity to sorb hydrocarbons, while at the same time they do not sorb water, making them well suited for sorbing hydrocarbons from the surface of a body of water). Accordingly, synthetic fibers are well suited for use as sorbents. Via empirical testing and analysis, applicants have determined that enhanced sorption efficiency can be obtained relative to other virgin polymer-based sorbents by controlling the fiber lengths and by using specially treated fibers.
Traditional virgin synthetic fibers have good adsorption properties with respect to hydrocarbons. Depending on the physical state or configuration of the fibers, virgin synthetic fiber-based sorbents may also have good absorbent properties. Adsorption is based on the attraction of material to the surface of a sorbent. Because of the natural chemical affinity between petroleum products and synthetic fibers, generally most synthetic fibers are reasonably effective at adsorbing hydrocarbons. In contrast, absorption is more a function of the physical state or configuration of the sorbent, because absorption involves the uptake of a material into a plurality of interstitial spaces within a matrix formed by the sorbent. A single, generally elongate extending fiber has no interstitial spaces (unless that fiber has been specially treated to enable the interior of the fiber to be accessible to a material, such as a dye), and cannot provide absorption of a material. However, a mass of fibers form a plurality of interstitial spaces in which absorption occurs. Such a mass can be beneficially employed as a sorbent or filter media.
Applicants have discovered that a mass of hydrophobic and lipophilic fibers having a specific range of lengths, when mixed together to form a matrix, have a greatly enhanced absorbency and serve as a very efficient sorbent. This matrix of fiber having a preferred range of lengths are referred to herein and in the claims that follow, as a xe2x80x9cwadded mass,xe2x80x9d or alternatively, as a xe2x80x9cwad.xe2x80x9d A wad preferably includes a substantial majority of shorter fibers and a minority of longer fibers (i.e., relative to a mid-length within the specific range of lengths). The long fibers act as a natural binder to give the resulting wad cohesiveness. The cohesiveness is sufficient so that the wad does not need to be encapsulated in a boom when used in treating oil spills. In moderate marine conditions, even normal wave action will not unduly disperse the wadded mass of sorbent, which is in sharp contrast to granular sorbents and non-wadded fiber based sorbents that typically require the use of encapsulating booms so that the respective sorbents are not unduly dispersed.
Empirical testing has determined that fiber lengths ranging from about 5 mm to about 100 mm are most preferred. A substantial majority of the fibers preferably range from about 5 mm to about 55 mm in length, and most preferably, about 70% of the fibers fall into the aforementioned range of length. The length of a minority of the fibers is in the range of from about 60 mm to about 100 mm in length, and most preferably, less than about 30% of the fibers are in this range. Regardless of the specific range employed, a substantial majority of the fibers must be relatively short to provide the desired large surface area, and the desired plurality of interstitial volumes. Also, regardless of the specific range of lengths of the fibers, sufficient relatively long fibers are required to enable the wadded mass to achieve a cohesiveness that resists dispersing the fibers when the wadded mass is exposed to a moderate wave action. Such dispersion is not desired, as widely dispersed sorbents are much more difficult to recover.
The ratio of short fibers to long fibers in the wadded mass is important in providing a high efficiency sorbent and filter media. A majority of short fibers increase sorbency by increasing the total surface area of the sorbent and by ensuring that the wadded mass includes a larger volume of interstitial spaces for absorption of a material. However, if only short fiber lengths are employed, the resulting mass of short fibers will be too easily dispersed by wind or wave action, and very little interstitial spaces will be available for absorption of hydrocarbons. Thus, a mass of only the short fibers would be difficult to recover and would be a less efficient sorbent, as very little absorption would take place. The only mechanism available for removing hydrocarbons in such a dispersed mass of only short fibers would be adsorption. Sufficient long fibers must be included to enable the wadded mass to be achieved, in accord with the present invention.
It has also been empirically determined that delustered synthetic fibers are more efficient sorbents than synthetic fibers that have not been delustered. Normally, virgin synthetic fibers are delustered when the fibers are to be used in fabrics. The delustering removes the inherent shininess of a synthetic fiber. Sometimes, a high luster in textiles is considered by consumers to look xe2x80x9ccheap,xe2x80x9d so a low-luster finish will enhance the richness of a particular fabric or carpeting. Because this is an aesthetic concern, as opposed to a functional concern, virgin synthetic fibers employed for sorbents are not delustered. Empirical results indicate that sorption by the delustered synthetic fibers of the present invention occurs extremely rapidly. As will be discussed in detail in the examples provided below, under controlled conditions, delustered synthetic fibers sorbed 9.5 times their own weight of oil in only about 10 seconds.
The delustering process appears to enhance the sorbent effectiveness of a fiber in several ways. First, the delustering process works by xe2x80x9cscuffingxe2x80x9d the surface of individual fibers, to reduce their sheen. This scuffing step results in rough fiber surfaces, and an individual fiber with a rough surface will have significantly more surface area than a fiber of the same size that has a smooth (or lustrous) surface. The increased surface area not only increases adsorption per fiber, but the rough surface of the fibers also increases the amount of interstitial volume available for absorption. The rough surface provides fiber-to-fiber traction, which further enhances the ability of a plurality of fibers to cohesively join together in the wadded mass described above. As indicated above, the wadded mass configuration provides significant interstitial volume that enhances absorption. The delustering process substantially enhances the sorbency of synthetic fibers, and it is preferable to employ a wadded mass of delustered hydrophobic and lipophilic fibers for the present invention. A common method of delustering fibers is to treat synthetic fibers with titanium dioxide.
Yet another aspect of the present invention is directed to a method of recycling waste fiber scrap into a sorbent product. Whole cloth is often recycled into other cloth applications. A large percentage of the used clothing that is recycled is reused as clothing and is often shipped overseas for use in third-world countries. A surprisingly efficient collection and distribution system enables a used, but still serviceable pair of pants from the United States to be shipped to a third-world country and sold at a cost significantly lower than a locally produced garment. Cloth is also recycled into wiping rags for industry and engineering applications. Almost 50% of recycled textiles are recycled back into clothing. About 20% become wiping and polishing cloths, and another 25% are regeneratedxe2x80x94converted back into fiber. Little of this fiber (referred to as xe2x80x9cshoddyxe2x80x9d) is currently being re-spun into new textiles, because such regenerated fibers are weaker than virgin fibers, resulting in a lower quality fabric. Instead, shoddy is often used in lower value applications such as for furniture stuffing or insulation in vehicles. However, the demand for shoddy, particularly shoddy that is primarily synthetic fiber (known as xe2x80x9cpoly shoddyxe2x80x9d), is generally significantly less than the available supply. In many areas of the country, rag mills are forced to dispose of poly shoddy in municipal landfills, at costs of up to five cents a pound.
In most of the conventional uses of shoddy, fiber length and its affect on the resulting matrix of the shredded fabric is not critical. Indeed, most shoddy is pressed into felt or other non-woven fabric, often after being impregnated with binders and adhesives. Generally, the fabric is processed to remove buttons and zippers, and the fabric is then shredded to a more or less fibrous state. In one aspect of the present invention, this traditionally processed poly shoddy can be used in encapsulating booms and pillows as a sorbent material. The fibers in the poly shoddy will already be substantially delustered, as most fabrics are made from delustered fiber. However, it is anticipated, and empirical testing has verified this to be true, that the sorbent efficiency of poly shoddy can be improved by applying more stringent processing steps than are normally required for generating shoddy.
One aspect of the present invention calls for manipulating the shredding process to control the fiber lengths achieved. As noted above, the majority of the fibers are preferably relatively short, from about 5 mm to about 50 mm in length. Preferably, more than about 70% of the fibers are within this range. A minority of the fibers must be relatively long, to enable the wadded mass described above to be achieved. The wadded mass configuration includes so much interstitial space that fibers in the wadded mass configuration are significantly more sorbent than the same fibers in a more planar configuration, such as a mat, due to the absorption occurring in the interstitial spaces. Preferably the relatively long fibers are from about 60 mm to about 100 mm in length, and comprise less than about 30% of the fibers.
The exact method used for controlling fiber length is a function of the equipment employed to process the synthetic fabric. In general, additional processing time will be required to achieve the desired dimensions. Note that for traditional uses of shoddy, it is preferable to minimize processing time, even if not all the fabric is completely reduced to fiber. In the present invention, the more complete the transformation from fabric to fiber, the more efficient the sorbent will be. It should also be noted that up to approximately ten percent by weight of the wadded mass can comprise non-synthetic fiber, such as cotton and cellulose fibers, without reducing the sorbent power of a wadded mass. Indeed, empirical testing has determined that the presence of small amounts of hydrophilic fibers is actually beneficial. Thus, an additional requirement with respect to the conventional poly shoddy manufacturing process is to presort the material being processed, to ensure that the desired blend or ratio of synthetic to non-synthetic fiber is achieved. It has been determined that up to 10% non-synthetic fiber is desirable. The presorting will be accomplished by hand, by technicians who can generally determine whether a textile is synthetic or non-synthetic by touch. Preferably the presorting will also be employed to remove undesirable non-synthetic textiles, such as vinyl textiles, or bulky textiles, such as sleeping bags, from the textiles that will be shredded.
One characteristic of conventionally processed poly shoddy is the presence of xe2x80x9cflagsxe2x80x9d or xe2x80x9cbitsxe2x80x9d in the final product. These flags and bits, generally quadrilateral in shape, represent portions of a textile item that have been reduced in size, but not to the fiber level. Such flags or bits can range in size from relatively small (fractions of an inch in dimension) to relatively large (over a foot in dimension), and their presence generally does not interfere with conventional uses of shoddy (for example, a furniture stuffing or to produce carpet pads). However, in the present invention, the presence of such flags reduces the amount of fiber present in a wadded mass, thereby reducing the sorbency of the product. Accordingly, it is desirable for the conventional poly shoddy producing process to be controlled to reduce the amount of flags or bits present in the final product.
A final aspect of the present invention is directed toward the use of a mass of delustered hydrophobic and lipophilic fibers as a filter media. In one embodiment, the mass of delustered hydrophobic and lipophilic fibers are processed into the previously described wadded mass by controlling the relative length of individual fibers. In another embodiment, the mass of delustered hydrophobic and lipophilic fibers is configured into a non-woven pad that is used as a filter. While such a non-woven pad lacks the extensive interstitial volume present in a wadded mass, the delustered fibers still provide an excellent filter media. When the delustered hydrophobic and lipophilic fibers are produced from textile waste, such pads can be produced at a low cost and can be employed as filter media or sorbents. Small pads can be fabricated for use with small spills, or large pads, referred to as blankets, can also be produced for use in cleaning up larger spills of petroleum products.